26 Aug
2020
26 Aug
'20
6:09 p.m.
On Wed, Aug 26, 2020 at 9:59 AM Noel Chiappa <jnc(a)mercury.lcs.mit.edu>
wrote:
This quirk of the PDP-11 is why I still prefer post-increment and
pre-decrement in my code... even though there's no chance in hades that my
code will ever run there...
Warner
From: John
Cowan
That's always true on the PDP-11 and Vax ...
because the processor
architecture (which has pre-increment and post-decrement
instructions,
but not their counterparts)
After Doug's message, I carefull re-read this, and I'm not sure it's
correct?
The PDP-11 has pre-decrement and post-increment, not the other way around
(as
above) - unless I'm misunderstanding what you meant by those terms?
That's why:
*p++ = 0;
turns (if p is in R2) into
CLR (R2)+
R2 is used, and then incremented after it has been used.